Field of the Invention
This invention relates to a flashmatic device for photographic programmed shutters having sectors which serve also as diaphragm blades.
Especially in the case of a camera with a built-in flash device (hereinafter referred to simply as "flash" for brevity), the flash is often used even in daylight as corrective lighting for a back-lighted subject or as an auxiliary illumination source. There have thus far been made various proposals with regard to daylight flashmatic shooting (hereinafter referred to as "daylight synchronizaiton") by programmed shutters to which the present invention is directed, namely, programmed shutters of the type in which sectors serving also as diaphragm blades are gradually opened with the lapse of time. One effective method is disclosed in Japanese Patent Publication No. 57-54777, in which the flash is triggered and fired at a time point when the opening shutter blades reach a diaphragm setting suitable for flashmatic shooting according to the subject in the course of opening the aperture. According to this patent publication, a first electronic signal is produced during a time period in which the gradually opened shutter reaches the diaphragm setting as determined according to the distance to the subject, triggering the flash by the first electric signal or a second shutter closing electric signal whichever is produced earlier. However, actually the shutter begins to close with a time delay of several ms from the time point at which the shutter closing signal is produced, so that in the case of shooting in daylight the second electric signal is produced considerably earlier than the time point when the maximum aperture is reached, failing to synchronize the flash. There is also a possiblity of firing the flash prematurely before the shutter begins to open, under paticular conditions, for example, when shooting a back-lighted figure beside a window.